Plants are important source of different secondary metabolites with expressed bioactivity. These compounds can be used as specific markers in chemotaxonomy for some plant species/genus/families providing unambiguous information for botanists or chemists in order to determine or to fulfill detailed chemical profile for some endemic or well-known species. It is very common that plant bioactive compounds express antioxidant properties with good ability to quench and neutralize reactive oxygen (ROS) or nitrogen (RNS) species in cells as well as to influence on some enzyme’s activity. In that way they can provide protective and positive effects in plants as well as in human body. Because of that there is a growing interest for its application as functional food ingredients or as possible medicine for some therapeutic purposes. In addition, application of some plants in folklore medicine is widespread all around the world. Advances in analytical technology have greatly accelerated the discovery of bioactive molecules or analogs. In that sense, this Special Issue is intended to collect some recent researches regarding to these topics and to provide new data about current status of scientific knowledge.